A turbine is a rotary engine that extracts energy from a fluid flow. The simplest turbines have one moving part, a rotor assembly, which is a shaft with a number of blades attached along its circumference. Moving fluid acts on the blades, or the blades react to the flow, so that they rotate and impart energy to the rotor.
Power plants usually use steam or gas turbines connected to a generator for electrical power generation. A gas turbine usually has an upstream compressor coupled to a downstream turbine, and a combustion chamber in-between. Energy is added to the gas stream in the combustor, where compressed air is mixed with fuel and ignited. Combustion increases temperature, velocity and volume of the gas flow, which is subsequently directed over the turbine's blades spinning the turbine and powering the combustor and any connected device.
Steam turbines use pressurized steam from e.g. a steam generator as its working fluid. To increase thermal efficiency, the steam can be expanded in multiple turbine stages. Here, steam flow exits from a high pressure section of the turbine and is returned to the boiler where additional superheat is added. The steam then goes back into an intermediate pressure section of the turbine and continues its expansion.
Especially in low pressure sections of turbines, large back-end blades are susceptible to vibratory excitation. In order to limit the amplitudes occurring in various situations and to prevent damage due to strong vibration, vibrational dampers are used in some designs. This can be achieved by e.g. solid body frictional damping between turbine blades, which limits said vibrations. However, allowing friction to damp vibration requires relatively loose contact of adjacent turbine blades, reducing the stability of the turbine blade system.